Titanium

How Products Are Made
COPYRIGHT 1996 Gale Research Inc.

Titanium

Background

Titanium is known as a transition metal on the periodic table of elements denoted by the symbol Ti. It is a lightweight, silver-gray material with an atomic number of 22 and an atomic weight of 47.90. It has a density of 4510 kg/m3, which is somewhere between the densities of aluminum and stainless steel. It has a melting point of roughly 3,032°F (1,667°C) and a boiling point of 5,948°F (3,287 C). It behaves chemically similar to zirconium and silicon. It has excellent corrosion resistance and a high strength to weight ratio.

Titanium is the fourth most abundant metal making up about 0.62% of the earth's crust. Rarely found in its pure form, titanium typically exists in minerals such as anatase, brookite, ilmenite, leucoxene, perovskite, rutile, and sphene. While titanium is relatively abundant, it continues to be expensive because it is difficult to isolate. The leading producers of titanium concentrates include Australia, Canada, China, India, Norway, South Africa, and Ukraine. In the United States, the primary titanium producing states are Florida, Idaho, New Jersey, New York, and Virginia.

Thousands of titanium alloys have been developed and these can be grouped into four main categories. Their properties depend on their basic chemical structure and the way they are manipulated during manufacture. Some elements used for making alloys include aluminum, molybdenum, cobalt, zirconium, tin, and vanadium. Alpha phase alloys have the lowest strength but are formable and weldable. Alpha plus beta alloys have high strength. Near alpha alloys have medium strength but have good creep resistance. Beta phase alloys have the highest strength of any titanium alloys but they also lack ductility.

The applications of titanium and its alloys are numerous. The aerospace industry is the largest user of titanium products. It is useful for this industry because of its high strength to weight ratio and high temperature properties. It is typically used for airplane parts and fasteners. These same properties make titanium useful for the production of gas turbine engines. It is used for parts such as the compressor blades, casings, engine cowlings, and heat shields.

Since titanium has good corrosion resistance, it is an important material for the metal finishing industry. Here it is used for making heat exchanger coils, jigs, and linings. Titanium's resistance to chlorine and acid makes it an important material in chemical processing. It is used for the various pumps, valves, and heat exchangers on the chemical production line. The oil refining industry employs titanium materials for condenser tubes because of corrosion resistance. This property also makes it useful for equipment used in the desalinization process.

Titanium is used in the production of human implants because it has good compatibility with the human body. One of the most notable recent uses of titanium is in artificial hearts first implanted in a human in 2001. Other uses of titanium are in hip replacements, pacemakers, defibrillators, and elbow and hip joints.

Finally, titanium materials are used in the production of numerous consumer products. It is used in the manufacture of such things as shoes, jewelry, computers, sporting equipment, watches, and sculptures. As titanium
dioxide, it is used as a white pigment in plastic, paper, and paint. It is even used as a white food coloring and as a sunscreen in cosmetic products.

History

Most historians credit William Gregor for the discovery of titanium. In 1791, he was working with menachanite (a mineral found in England) when he recognized the new element and published his results. The element was rediscovered a few years later in the ore rutile by M. H. Klaproth, a German chemist. Klaproth named the element titanium after the mythological giants, the Titans.

Both Gregor and Klaproth worked with titanium compounds. The first significant isolation of nearly pure titanium was accomplished in 1875 by Kirillov in Russia. Isolation of the pure metal was not demonstrated until 1910 when Matthew Hunter and his associates reacted titanium tetrachloride with sodium in a heated steel bomb. This process produced individual pieces of pure titanium. In the mid 1920s, a group of Dutch scientists created small wires of pure titanium by conducting a dissociation reaction on titanium tetraiodide.

These demonstrations prompted William Kroll to begin experimenting with different methods for efficiently isolating titanium. These early experiments led to the development of a process for isolating titanium by reduction with magnesium in 1937. This process, now called the Kroll process, is still the primary process for producing titanium. The first products made from titanium were introduced around the 1940s and included such things as wires, sheets, and rods.

While Kroll's work demonstrated a method for titanium production on a laboratory scale, it took nearly a decade more before it could be adapted for large-scale production. This work was conducted by the United States Bureau of Mines from 1938 to 1947 under the direction of R. S. Dean. By 1947, they had made various modifications to Kroll's process and produced nearly 2 tons of titanium metal. In 1948, DuPont opened the first large scale manufacturing operation.

This large scale manufacturing method allowed for the use of titanium as a structural material. In the 1950s, it was used primarily by the aerospace industry in the construction of aircraft. Since titanium was superior to steel for many applications, the industry grew rapidly. By 1953, annual production had reached 2 million lb (907,200 kg) and the primary customer for titanium was the United States military. In 1958, demand for titanium dropped off significantly because the military shifted its focus from manned aircraft to missiles for which steel was more appropriate. Since then, the titanium industry has had various cycles of high and low demand. Numerous new applications and industries for titanium and its alloys have been discovered over the years. Today, about 80% of titanium is used by the aerospace industry and 20% by non-aerospace industries.

Raw Materials

Titanium is obtained from various ores that occur naturally on the earth. The primary ores used for titanium production include ilmenite, leucoxene, and rutile. Other notable sources include anatase, perovskite, and sphene.

Ilmenite and leucoxene are titaniferous ores. Ilmenite (FeTiO3) contains approximately 53% titanium dioxide. Leucoxene has a similar composition but has about 90% titanium dioxide. They are found associated with hard rock deposits or in beaches and alluvial sands. Rutile is relatively pure titanium dioxide (TiO2). Anatase is another form of crystalline titanium dioxide and has just recently become a significant commercial source of titanium. They are both found primarily in beach and sand deposits.

Perovskite (CaTiO3) and sphene (CaTi-SiO5) are calcium and titanium ores. Neither of these materials are used in the commercial production of titanium because of the difficulty in removing the calcium. In the future, it is likely that perovskite may be used commercially because it contains nearly 60% titanium dioxide and only has calcium as an impurity. Sphene has silicon as a second impurity that makes it even more difficult to isolate the titanium.

In addition to the ores, other compounds used in titanium production include chlorine gas, carbon, and magnesium.

The ManufacturingProcess

Titanium is produced using the Kroll process. The steps involved include extraction, purification, sponge production, alloy creation, and forming and shaping. In the United States, many manufacturers specialize in different phases of this production. For example, there are manufacturers that just make the sponge, others that only melt and create the alloy, and still others that produce the final products. Currently, no single manufacturer completes all of these steps.

Extraction

1 At the start of production, the manufacturer receives titanium concentrates from mines. While rutile can be used in its natural form, ilmenite is processed to remove the iron so that it contains at least 85% titanium dioxide. These materials are put in a fluidized-bed reactor along with chlorine gas and carbon. The material is heated to 1,652°F (900°C) and the subsequent chemical reaction results in the creation of impure titanium tetrachloride (TiCl4) and carbon monoxide. Impurities are a result of the fact that pure titanium dioxide is not used at the start. Therefore the various unwanted metal chlorides that are produced must be removed.

Purification

2 The reacted metal is put into large distillation tanks and heated. During this step, the impurities are separated using fractional distillation and precipitation. This action removes metal chlorides including those of iron, vanadium, zirconium, silicon, and magnesium.

Production of the sponge

3 Next, the purified titanium tetrachloride is transferred as a liquid to a stainless steel reactor vessel. Magnesium is then added and the container is heated to about 2,012°F (1,100°C). Argon is pumped into the container so that air will be removed and contamination with oxygen or nitrogen is prevented. The magnesium reacts with the chlorine producing liquid magnesium chloride. This leaves pure titanium solid since the melting point of titanium is higher than that of the reaction.

4 The titanium solid is removed from the reactor by boring and then treated with water and hydrochloric acid to remove excess magnesium and magnesium chloride. The resulting solid is a porous metal called a sponge.

Alloy creation

5 The pure titanium sponge can then be converted into a usable alloy via a consumable-electrode arc furnace. At this point, the sponge is mixed with the various alloy additions and scrap metal. The exact proportion of sponge to alloy material is formulated in a lab prior to production. This mass is then pressed into compacts and welded together, forming a sponge electrode.

6 The sponge electrode is then placed in a vacuum arc furnace for melting. In this water-cooled, copper container, an electric arc is used to melt the sponge electrode to form an ingot. All of the air in the container is either removed (forming a vacuum) or the atmosphere is filled with argon to prevent contamination. Typically, the ingot is
remelted one or two more times to produce a commercially acceptable ingot. In the United States, most ingots produced by this method weigh about 9,000 lb (4,082 kg) and are 30 in (76.2 cm) in diameter.

7 After an ingot is made, it is removed from the furnace and inspected for defects. The surface can be conditioned as required for the customer. The ingot can then be shipped to a finished goods manufacturer where it can be milled and fabricated into various products.

Byproducts/Waste

During the production of pure titanium a significant amount of magnesium chloride is produced. This material is recycled in a recycling cell immediately after it is produced. The recycling cell first separates out the magnesium metal then the chlorine gas is collected. Both of these components are reused in the production of titanium.

The Future

Future advances in titanium manufacture are likely to be found in the area of improved ingot production, the development of new alloys, the reduction in production costs, and the application to new industries. Currently, there is a need for larger ingots than can be produced by the available furnaces. Research is ongoing to develop larger furnaces that can meet these needs. Work is also being done on finding the optimal composition of various titanium alloys. Ultimately, researchers hope that specialized materials with controlled microstructures will be readily produced. Finally, researchers have been investigating different methods for titanium purification. Recently, scientists at Cambridge University announced a method for producing pure titanium directly from titanium dioxide. This could substantially reduce production costs and increase availability.

Titanium (revised)

TITANIUM (REVISED)

Note: This article, originally published in 1998, was updated in 2006 for the eBook edition.

Overview

Titanium is found in the middle of the periodic table. The periodic table is a chart that shows how chemical elements are related to one another. Titanium is a transition metal and is part of Group 4 (IVB).

Titanium was one of the first elements to be discovered by modern chemists. The "modern" chemistry period begins after the middle of the eighteenth century. That period is chosen because it is the first time that the basic concepts of modern chemistry were developed.

Titanium was discovered by English clergyman William Gregor (1761-1817). Gregor studied minerals as a hobby. He did not think of himself as a chemist, and yet his research led to the discovery of titanium.

SYMBOL
Ti

ATOMIC NUMBER
22

ATOMIC MASS
47.88

FAMILY
Group 4 (IVB)
Transition metal

PRONUNCIATION
ty-TAY-nee-um

Titanium and its compounds have become very important in modern society. The metal is widely used in a variety of alloys. An alloy is made by melting and mixing two or more metals. The mixture has properties different from those of the individual metals. Titanium alloys are used in aircraft, spacecraft, jewelry, clocks, armored vehicles, and in the construction of buildings.

Discovery and naming

Gregor discovered titanium while he was studying a mineral found near his home. He was able to identify most of the mineral, but he found one part that he could not identify. He decided it was a new substance, but did not continue his research. Instead, he wrote a report and left it to professional chemists to find out more about the material.

Today, we know that the material Gregor found is a mineral called ilmenite. Ilmenite is made of iron, oxygen, and titanium. Its chemical formula is FeTiO3. Even though Gregor did not complete his study of ilmenite, he is usually given credit for the discovery of titanium.

Surprisingly, most chemists paid little attention to Gregor's report. Four years later, German chemist Martin Heinrich Klaproth (1743-1817) decided to study ilmenite. Klaproth believed that Gregor had been correct and that ilmenite truly did contain a new element. Klaproth suggested the name titanium, in honor of the Titans. The Titans were mythical giants who ruled the Earth until they were overthrown by the Greek gods. Klaproth reminded everyone that Gregor should receive credit for having discovered the element.

Klaproth was never able to produce pure titanium from ilmenite, only titanium dioxide (TiO2). It was not until 1825 that even impure titanium metal was produced. Swedish chemist Jöns Jakob Berzelius (1779-1848) accomplished this task.

Physical properties

Pure titanium metal can exist as a dark gray, shiny metal or as a dark gray powder. It has a melting point of 1,677°C (3,051°F) and a boiling point of 3,277°C (5,931°F). Its density is 4.6 grams per cubic centimeter. Titanium metal is brittle when cold and can break apart easily at room temperature. At higher temperatures, it becomes malleable and ductile. Malleable means capable of being hammered into thin sheets. Ductile means capable of being drawn into thin wires.

Titanium has an interesting physical property. Small amounts of oxygen or nitrogen, make it much stronger.

Chemical properties

In general, titanium tends to be quite unreactive. It does not combine with oxygen at room temperature. It also resists attack by acids, chlorine, and other corrosive agents. A corrosive agent is a material that tends to vigorously react or eat away at something.

Titanium becomes more reactive at high temperatures. It can actually catch fire when heated in the presence of oxygen.

Occurrence in nature

Titanium is a very common element. It is the ninth most abundant element in the Earth's crust. Its abundance is estimated to be about 0.63 percent. That places titanium just above hydrogen and just below potassium among elements present in the earth.

Titanium metal is brittle when cold and can break apart easily at room temperature.

The most common mineral sources of titanium are ilmenite, rutile, and titanite. Titanium is also obtained from iron ore slags. Slag is an earthy material that floats to the top when iron is removed from iron ore.

Isotopes

Five naturally occurring isotopes of titanium exist. They are titanium-46, titanium-47, titanium-48, titanium-49, and titanium-50. The most abundant of these is titanium-48. It makes up about 75 percent of all titanium found in nature. Isotopes are two or more forms of an element. Isotopes differ from each other according to their mass number. The number written to the right of the element's name is the mass number. The mass number represents the number of protons plus neutrons in the nucleus of an atom of the element. The number of protons determines the element, but the number of neutrons in the atom of any one element can vary. Each variation is an isotope.

Four artificial isotopes of titanium have also been made. These are all radioactive. A radioactive isotope is one that breaks apart and gives off some form of radiation. Radioactive isotopes are produced when very small particles are fired at atoms. These particles stick in the atoms and make them radioactive.

None of the radioactive isotopes of titanium has any commercial applications.

Extraction

The methods used to obtain titanium are similar to those used for other metals. One way to make the metal is to heat one of its compounds with another metal, such as magnesium:

Another approach is to pass an electric current through a molten (melted) compound of titanium:

Uses

By far the most important use of titanium is in making alloys. The metal is most commonly added to steel. It adds strength to the steel and makes it more resistant to corrosion (rusting). Titanium also has another advantage in alloys. Its density is less than half that of steel. So a steel alloy containing titanium weighs less, pound-for-pound, than does the pure steel alloy.

These properties explain why titanium steel is so desirable for spacecraft and aircraft applications. In fact, about 65 percent of all titanium sold is used in aerospace applications. Titanium alloys are used in the airframes (bodies) and engines of aircraft and spacecraft. Other uses are in armored vehicles, armored vests, and helmets, in jewelry, eyeglasses, bicycles, golf clubs, and other sports equipment; in specialized dental implants; in power-generating plants and other types of factories; and in roofs, faces, columns, walls, ceilings, and other parts of buildings.

Titanium alloys have also become popular in body implants, such as artificial hips and knees. These alloys are light, strong, long-lasting, and biocompatible. Biocompatible means that the alloy does not cause a reaction when placed into the body.

Titanium tetrachloride combines with moisture in the air to form a dense white cloud. Skywriters use titanium tetrachloride to form letters in the sky.

Compounds

The most important compound of titanium is titanium dioxide (TiO2). In 1996, 1,230,000 metric tons of this compound was produced in the United States. Titanium dioxide is a dense white powder with excellent hiding power. That term means that anything beneath it cannot be seen well. This property accounts for the major use of titanium dioxide: making white
paint. Titanium dioxide paint is a good choice for painting over old wallpaper or dark paints because it covers so well. In 1996, about half of the titanium dioxide produced in the United States was used in paints.

About 40 percent of all titanium dioxide used in the United States goes into paper and plastic materials. Titanium dioxide gives "body" to paper and makes it opaque (unable to see through it). Other uses are in floor coverings, fabrics and textiles, ceramics, ink, roofing materials, and catalysts in industrial operations. A catalyst is a substance used to speed up or slow down a chemical reaction without undergoing any change itself.

Another interesting compound is titanium tetrachloride (TiCl4). Titanium tetrachloride is a clear, colorless liquid when kept in a sealed container. However, it changes dramatically when exposed to the air. It combines with moisture in the air to
form a dense white cloud. Skywriters use titanium tetrachloride to form letters in the sky. The compound is also used to make smokescreens. Smoke effects used in motion pictures and television programs sometimes are produced with titanium tetrachloride.

Health effects

Titanium appears to have no harmful effects on plants or humans. It has also not been shown to have any role in maintaining good health.

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titanium

The Columbia Encyclopedia, 6th ed.

Copyright The Columbia University Press

titanium (tītā´nēəm, tĬ–) [from Titan], metallic chemical element; symbol Ti; at. no. 22; at. wt. 47.867; m.p. 1,675°C; b.p. 3,260°C; sp. gr. 4.54 at 20°C; valence +2, +3, or +4. Titanium is a lustrous silver-white metal that exhibits allotropy; below about 880°C it has a hexagonal crystalline structure, but above that temperature it changes to a cubic crystalline structure. The metal is strong and has low density; it is ductile when pure and malleable when heated. Its chemical properties resemble those of zirconium, the element below it in Group 4 of the periodic table. When heated, it ignites and burns in air. It is the only element that burns in nitrogen. It is very corrosion resistant and is unattacked by most acids, by moist chlorine gas, or by common salt solutions. Several of its compounds are commercially important. Pure crystalline titanium dioxide (titania) is used as a gemstone. The dioxide is also widely used as a paint pigment, especially for exterior paints. Titanates are formed from the dioxide, which is weakly acidic. An interesting example is barium titanate, which is piezoelectric and can be used as a transducer for the interconversion of sound and electricity. Titanium tetrachloride, a liquid, fumes in moist air; it is used for smoke screens and in skywriting. It is also an important catalyst in the polymerization of olefins. Titanium esters, formed by the reaction of the tetrachloride with alcohols, are used as waterproofing agents on fabrics. Titanic sulfate is used as a textile mordant. Titanium metal and its alloys are light in weight and have very high tensile strength, even at high temperatures. These metals are utilized in aircraft and spacecraft construction and in naval ships, guided missiles, and lightweight armor plate for tanks. Titanium compounds are widely distributed in nature. Rutile, the native dioxide, and ilmenite, which contains, besides titanium, iron and oxygen, are its chief sources. The metal cannot be produced by reduction of the dioxide, because titanium reacts with both oxygen and nitrogen at high temperatures. One method used consists in passing chlorine over ilmenite or rutile, heated to redness with carbon. Titanium tetrachloride, which is formed, is condensed, purified by fractional distillation, and then reduced with molten magnesium at 800°C in an atmosphere of argon. Titanium is present in the sun and certain other stars, in meteorites, and on the moon. Titanium dioxide causes the star effect in certain sapphires and rubies. The element was discovered (1791) by William Gregor and rediscovered (1795) by M. H. Klaproth, who gave it its present name.

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Titanium

Titanium

Titanium is a strong, lightweight, silver-white metal . It was discovered in 1791 by Reverend William Gregor, a British cleric who established its presence in the mineral menachanite. The German chemist Martin Heinrich Klaproth named the element after the Titans, the sons of the earth goddess in Greek mythology. Pure titanium was not isolated until 1910, when American metallurgist Matthew A. Hunter heated titanium (IV) chloride (TiCl4) with sodium at temperatures between 700°C and 800°C.

As the ninth most common element in the earth's crust, titanium occurs at an abundance of 6,600 parts per million (ppm) or 5.63 grams per kilogram. Its chief sources are the minerals ilmenite (FeTiO3), rutile (TiO2), and sphene (CaTiSiO5); ilmenite is the source of approximately 90 percent of titanium produced. Titanium is largely produced in the United States, Canada, Russia, Japan, Kazakhstan, Germany, France, and Spain.

The most common isotope of titanium is 48Ti, which has a natural abundance of 73.72 percent. Four other stable isotopes exist: 46Ti (8.25%), 47Ti (7.44%), 49Ti (5.41%), and 50Ti (5.18%). Most titanium is used in its dioxide (TiO2) or metallic form.

Titanium's physical properties (high melting temperature, resistance to corrosion, strength, light weight) make it an ideal additive to alloys used by the aerospace industry in rockets and jet aircraft, for ship components that are exposed to seawater, and for biomedical implants such as artificial joints or pacemakers. Titanium dioxide is utilized as a white pigment in paint, paper, plastics, and cosmetics. It is also used in some sunscreens because of its ability to absorb ultraviolet (UV) light.

titanium

titanium (symbol Ti) Lustrous, silver-grey, metallic element, one of the transition elements. A common element, it is found in many minerals, chief sources being ilmenite and rutile. Resistant to corrosion and heat, it is used in steels and other alloys, especially in aircraft, spacecraft and guided missiles where strength must be combined with lightness. It was discovered in 1791 by the English mineralogist William Gregor (1761–1817). Properties: at.no. 22; r.a.m. 47.90; r.d. 4.54; m.p. 1660°C (3020°F); b.p. 3287°C (5949°F); most common isotope Ti48 (73.94%).

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